XMLHttpRequest: readystatechange event
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
Note: This feature is available in Web Workers, except for Service Workers.
The readystatechange event is fired whenever the readyState property of the XMLHttpRequest changes.
Warning: This should not be used with synchronous requests and must not be used from native code.
Syntax
Use the event name in addEventListener():
js
addEventListener("readystatechange", (event) => { })
Alternatively, assign to the event handler property of the interface:
js
onreadystatechange = (event) => { }
Event type
A generic Event with no added properties.
Examples
js
const xhr = new XMLHttpRequest();
const method = "GET";
const url = "https://developer.mozilla.org/";
xhr.open(method, url, true);
xhr.onreadystatechange = () => {
// In local files, status is 0 upon success in Mozilla Firefox
if (xhr.readyState === XMLHttpRequest.DONE) {
const status = xhr.status;
if (status === 0 || (status >= 200 && status < 400)) {
// The request has been completed successfully
console.log(xhr.responseText);
} else {
// Oh no! There has been an error with the request!
}
}
};
xhr.send();
Specifications
| Specification |
|---|
| XMLHttpRequest # event-xhr-readystatechange |
| XMLHttpRequest # handler-xhr-onreadystatechange |